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PubMed2002

Feedback on hypothalamic TRH transcription is dependent on thyroid hormone receptor N terminus.

The beta thyroid hormone receptor (TRbeta), but not TRalpha1, plays a specific role in mediating T(3)-dependent repression of hypothalamic TRH transcription. To investigate the structural basis of isoform specificity, we compared the transcriptional regulation and DNA binding obtained with chimeric and N-terminally deleted TRs. Using in vivo transfection assays to follow hypothalamic TRH transcription in the mouse brain, we found that TRbeta1 and chimeras with the TRbeta1 N terminus did not affect either transcriptional activation or repression from the rat TRH promoter, whereas N-terminally deleted TRbeta1 impaired T(3)-dependent repression. TRalpha1 or chimeras with the TRalpha1 N terminus reduced T(3)-independent transcriptional activation and blocked T(3)-dependent repression of transcription. Full deletion of the TRalpha1 N terminus restored ligand-independent activation of transcription. No TR isoform specificity was seen after transcription from a positive thyroid hormone response element. Gel mobility assays showed that all TRs tested bound specifically to the main negative thyroid hormone response element in the TRH promoter (site 4). Addition of neither steroid receptor coactivator 1 nor nuclear extracts from the hypothalamic paraventricular nuclei revealed any TR isoform specificity in binding to site 4. Thus N-terminal sequences specify TR T(3)-dependent repression of TRH transcription but not DNA recognition, emphasizing as yet unknown neuron-specific contributions to protein-promoter interactions in vivo.

Animals↗
PubMed2006

Unexpected peripheral markers of thyroid function in a patient with a novel mutation of the MCT8 thyroid hormone transporter gene.

The specific thyroid hormone transporter, MCT8, located on the X chromosome, has led to the identification a novel syndrome. The objective is to relate phenotype with several tissue-specific thyroid functions. A 1-year-old boy, who had severe psychological damage and low serum T4, had received l-T4 for 3 months. At admission, body length was normal but weight was low. Off therapy, serum TSH was mildly elevated, serum T4 and free T4 were low, and serum T3 and free T3 were high. Direct sequencing of the MCT8 gene revealed a single nucleotide change that resulted in a novel nonsense mutation at codon 261 (Q261X) in exon 3. Since serum T3 was high, peripheral markers of hyperthyroidism were looked for. Bone age was advanced, despite the presence of malnutrition and low T4. Serum SHBG, a marker of thyroid hormone action in liver, was markedly elevated. Markers of skeletal muscle catabolism, ammonemia and lactic acid, were found to be elevated. The phenotype of MCT 8 mutation might be explained by differences in the entry of thyroid hormones into different cells. In the presence of an inactive MCT8 transporter, the high blood T3 levels might not be enough to prevent brain damage early in life, while they seem to be able to induce a postnatal state of peripheral hyperthyroidism in other tissues, such as liver, bone and skeletal muscle.

Age Determination by Skeleton↗
PubMed1975

Pituitary unresponsiveness to thyrotropin-releasing hormone in thyrotoxic patients during chronic anti-thyroid drug therapy and in rats previously treated with excess thyroid hormone.

In an attempt to study pituitary-thyroid feedback control in thyrotoxic patients, TRH tests were performed in 10 thyrotoxic patients who were treated for varying intervals with propylthiouracil. Plasma TSH was undetectable before and after administration of 500 mug TRH in 7 patients (euthyroid or hypothyroid) after therapy for 1 to 4 months. Also, plasma TSH was undetectable before and after TRH in 3 patients who had been euthyroid for at least 6 months. To explore this abnormality, rats were made thyrotoxic by administering large doses of thyroxine or desiccated thyroid for 3 to 28 days. Discontinuation of thyroid hormone administration was followed by a significant but temporary fall of plasma thyroxine and triiodothyronine concentration below control levels. Duration of the low plasma thyroxine and triiodothyronine concentration was longer with the prolonged administration of thyroid hormone. Despite low plasma thyroxine and triiodothyronine concentrations, plasma TSH was below normal before and after administration of TRH. This unresponsiveness of the pituitary to TRH may be comparable to that found in thyrotoxic patients receiving antithyroid drugs for a certain period. Since this pituitary unresponsiveness to TRH in rats is due to a depletion of pituitary TSH content, it is suggested that depletion of pituitary TSH in thyrotoxic patients during antithyroid therapy is the cause of pituitary unresponsiveness to TRH.

Adult↗
PubMed2005

Iodothyronine deiodinases and the control of plasma and tissue thyroid hormone levels in hyperthyroid tilapia (Oreochromis niloticus).

Thyroid status is one of the most potent regulators of peripheral thyroid hormone metabolism in vertebrates. Despite this, the few papers that have been published concerning the role of thyroid hormones in the regulation of thyroid function in fish often offer conflicting data. We therefore set out to investigate the effects of tetraiodothyronine (thyroxine) (T4) or tri-iodothyronine (T3) supplementation (48 p.p.m.) via the food on plasma and tissue thyroid hormone levels as well as iodothyronine deiodinase (D) activities in the Nile tilapia (Oreochromis niloticus). T4 supplementation did not induce a hyperthyroid state and subsequently had no effects on the thyroid hormone parameters measured, with the liver as the sole notable exception. In T4-fed tilapias, the hepatic T4 levels increased substantially, and this was accompanied by an increase in in vitro type I deiodinase (D1) activity. Although the lack of effect of T4 supplementation could be partially explained by an inefficient uptake of T4 from the gut, our current data suggest that also the increased conversion of T4 into reverse (r)T3 by the D1 present in the liver plays an important role in this respect. In addition, T3 supplementation increased plasma T3 and decreased plasma T4 concentrations. T3 levels were also increased in the liver, brain, kidney, gill and white muscle, but without affecting local T4 concentrations. However, this increase in T3 availability remained without effect on D1 activity in liver and kidney. This observation, together with the 6-n-propylthiouracyl (PTU) insensitivity of the D1 enzyme in fish, sets the D1 in teleost fish clearly apart from its mammalian and avian counterparts. The changes in hepatic deiodinases confirm the role of the liver as an important T3-regulating tissue. However, the very short plasma half-life of exogenously administered T3 implies the existence of an efficient T3 clearing/degradation mechanism other than deiodination.

Animals↗
PubMed1997

Modulation of chronic excessive interleukin-6 production in multiple myeloma does not affect thyroid hormone concentrations.

Interleukin-6 (IL6) is believed to be involved in alterations of thyroid hormone metabolism in acute nonthyroidal illness. To evaluate the effects of IL6 on thyroid hormone metabolism in a chronic IL6-mediated disease, we measured thyroid hormone concentrations in multiple myeloma patients treated with intravenous anti-IL6 chimeric monoclonal antibodies ([cMabs] Kd = 6.25 x 10(-12) mol/L). Twelve patients were studied, receiving at least one complete treatment cycle of 14 days (daily dose: 5 mg, n = 3; 10 mg, n = 3; 20 mg, n = 3; and 40 mg, n = 3). Eight of them also completed a second treatment cycle of 14 days. Thyroid hormone concentrations were measured before, during, and after treatment with the anti-IL6 cMab. Even in the group with the lowest dosage, IL6 activity measured by the B9 bioassay was blocked completely. Compared with the reference ranges, 10 of 12 patients had one or more abnormal pretreatment values for thyroid hormone concentrations. Thyroid autoantibodies were negative in all patients. There was no correlation between thyroid hormone concentrations and IL6 levels, although plasma IL6 levels were increased in all but one subject. Moreover, neutralization of free IL6 by the anti-IL6 cMab did not affect thyroid hormone concentrations, although IL6-dependent C-reactive protein (CRP) levels decreased to undetectable levels in 11 of 12 patients. Two patients developed infectious complications resulting in increased free IL6 and CRP levels and in profound alterations of thyroid hormone levels consistent with an acute euthyroid sick syndrome. We conclude that IL6 is not a major determinant of thyroid hormone abnormalities in a chronic disease like multiple myeloma, but IL6 may be involved in thyroid hormone metabolism in acute diseases (probably in combination with other factors).

Aged↗
PubMed2004

Crystallization and preliminary X-ray diffraction studies of isoform alpha1 of the human thyroid hormone receptor ligand-binding domain.

Thyroid hormone receptors (TR) play critical roles in virtually all tissues. The TR ligand-binding domain (LBD) participates in important activities, such as transcriptional activation and repression, through conformational changes induced by hormone binding. Two crystal forms of isoform alpha1 of the human thyroid hormone receptor LBD (hTRalpha1) in complex with the thyroid hormones T3 and Triac were obtained. The hTRalpha1-T3 complex was crystallized in a previously unobserved crystal form (space group P2(1)2(1)2(1), a = 59.98, b = 80.80, c = 102.21 A), with diffraction patterns extending to 1.90 A resolution on a rotating-anode X-ray source, and in space group C2 (a = 117.54, b = 80.66, c = 62.55 A, beta = 121.04 degrees), with data extending to 2.32 A resolution. The hTRalpha1-Triac complex was also crystallized in the new space group P2(1)2(1)2(1), with unit-cell parameters a = 60.01, b = 80.82, c = 102.39 A; its resolution limit extended to 2.20 A on a home source. Phasing was carried out by the molecular-replacement method and structural refinement is currently in progress. The refined structures may provide insight into the design of new thyromimetics.

Crystallization↗
PubMed1986

Thyroid hormone receptors bind to defined regions of the growth hormone and placental lactogen genes.

The intracellular receptor for thyroid hormone is a protein found in chromatin. Since thyroid hormone stimulates transcription of the growth hormone gene through an unknown mechanism, the hypothesis that the thyroid hormone-receptor complex interacts with defined regions of this gene has been investigated in a cell-free system. Nuclear extracts from human lymphoblastoid IM-9 cells containing thyroid hormone receptors were incubated with L-3,5,3'-tri[125I]iodothyronine and calf thymus DNA-cellulose. Restriction fragments of the human growth hormone gene were added to determine their ability to inhibit labeled receptor binding to DNA-cellulose. These fragments encompassed nucleotide sequences from about three kilobase pairs upstream to about four kilobase pairs downstream from the transcription initiation site. The thyroid hormone-receptor complex bound preferentially to the 5'-flanking sequences of the growth hormone gene in a region between nucleotide coordinates -290 and -129. The receptor also bound to an analogous promoter region in the human placental lactogen gene, which has 92% nucleotide sequence homology with the growth hormone gene. These binding regions appear to be distinct from those that are recognized by the receptor for glucocorticoids, which stimulate growth hormone gene expression synergistically with thyroid hormone. The presence of thyroid hormone was required for binding of its receptor to the growth hormone gene promoter, suggesting that thyroid hormone renders the receptor capable of recognizing specific gene regions.

Base Sequence↗
PubMed2000

Regulation of the L1 cell adhesion molecule by thyroid hormone in the developing brain.

Thyroid hormone is essential for brain maturation, regulating neuronal differentiation and migration, myelination, and synaptogenesis. Mutations in the cell adhesion molecule L1 cause severe neurological abnormalities in humans. We studied the effect of thyroid hormone deprivation and administration on L1 expression. Northern and in situ hybridization studies showed that hypothyroidism induces a marked increase in L1 mRNA levels in the caudate putamen, cerebral cortex, amygdala, and some thalamic nuclei. L1 protein was overexpressed in embryonic and newborn hypothyroid rats in the caudate putamen, internal capsule, habenula, and neocortex. Later in development, an abnormally high L1 expression was found in the cortical and cerebellar white matter, corpus callosum, anterior commissure, thalamocortical projections, and striatal fiber tracts of hypothyroid animals. Thyroid hormone administration reversed the upregulation of L1 expression in vivo and in cultured cells. Thus, alterations of L1 expression may contribute to the profound abnormalities caused by hypothyroidism in the developing brain.

Animals↗
PubMed2006

Design and characterization of a thyroid hormone receptor alpha (TRalpha)-specific agonist.

Thyroid hormone is a classical endocrine signaling molecule that regulates a diverse array of physiological processes ranging from energy metabolism to cardiac performance. The active form of thyroid hormone, 3,5,3'-triiodo- l -thyronine or T 3 , exerts many of its actions through its receptor, the thyroid hormone receptor (TR), of which there are two subtypes for two isoforms: TRalpha 1 , TRalpha 2 , TRbeta 1 , and TRbeta 2 . Although TR isoforms, with the exception of TRbeta 2 , are expressed in all tissues, they display different patterns of expression in different tissues, giving rise to tissue-specific isoform actions. Currently, several TRbeta-selective agonists have been developed; however, TRalpha-selective agonists have remained elusive. Herein, we report the synthesis and biological evaluation of CO23, the first potent thyromimetic with TRalpha-specific effects in vitro and in vivo .

Animals↗
PubMed1992

Ligand-dependent synergy of thyroid hormone and retinoid X receptors.

The binding of thyroid hormone receptors to DNA is enhanced by heterodimerization with nuclear proteins. One such heterodimerization partner has recently been characterized as the retinoid X receptor. 9-cis-Retinoic acid has been identified as a natural ligand for retinoid X receptors, suggesting a potential receptor-mediated interaction between thyroid hormone and 9-cis-retinoic acid in the regulation of thyroid hormone-responsive genes. A transient cotransfection assay was used to test for such an interaction. When a complex thyroid hormone response element composed of both direct and inverted repeat hexamers was tested, these two ligands activated gene expression synergistically. In contrast, when the response element consisted only of directly repeated hexamers, unliganded retinoid X receptors enhanced thyroid hormone responsiveness, but 9-cis-retinoic acid induced no additional activation. The results suggest a unique mechanism to achieve differential suggest a unique mechanism to achieve differential thyroid hormone sensitivity of thyroid hormone-responsive genes within a cell. Genes with appropriate response elements will show amplification of the thyroid hormone response by 9-cis-retinoic acid in the presence of retinoid X receptors; other thyroid hormone-responsive genes will be influenced by retinoid X receptors, but not 9-cis-retinoic acid.

Animals↗
PubMed1989

Antagonism of thyroid hormone action by amiodarone in rat pituitary tumor cells.

A thyroid hormone antagonist has not been previously described. A number of thyroid hormone analogues have been shown to compete with [125I]triiodothyronine ([125I]T3) for binding to the intranuclear thyroid hormone receptor and to have agonist activity proportional to their affinities for the receptors. We report that the benzofuran amiodarone acts as a competitive antagonist to thyroid hormone action as defined by its dose-dependent ability to (a) bind to the thyroid hormone receptor and (b) inhibit T3-induced increases in growth hormone mRNA levels in a cultured rat pituitary cell line, GC cells. Like T3 itself, amiodarone also decreases transport of [125I]T3 across GC cell membranes. An analysis of the amiodarone structure suggests that this compound has certain similarities to T3. These findings hold promise for the development of other thyroid hormone antagonists for clinical use and for understanding thyroid hormone action.

Amiodarone↗
PubMed1975

The role of the pentose phosphate shunt in thyrotropin-induced thyroid hormone secretion: in vivo and vitro studies with 6-aminonicotinamide in mouse thyroids.

The possible role of the pentose phosphate shunt in thyroid hormone secretion was investigated in vivo and in vitro with mouse thyroid glands. Thyroidal endocytosis in response to TSH, a step of thyroid hormone secretion, was evaluated for its dependency upon the pentose phosphate shunt by using 6-aminonicotinamide (6-AN), an antimetabolite in the synthesis of pyridine nucleotides. Formation of 14CO2 from glucose labeled either in the C-1 or C-6 position was studied to estimate the pentose phosphate shunt activity. A dose of 6-AN markedly reduced oxidation of [1-14C]glucose but did not affect that of [6-14C]glucose induced by TSH. Concomitantly there was a marked decrease in thyroidal endocytotic response to TSH. These inhibitions by 6-AN were completely abolished by the pretreatment with nicotinamide. Methylene blue, which oxidizes NADPH and thus stimulates activity of the pentose shunt, significantly depressed thyroidal endocytosis in response to TSH in vitro. These inhibitions of colloid droplet formation by 6-AN or methylene blue were not manifested against dibutyryl cyclic AMP stimulation. Furthermore, a dose of 6-AN, which seems to inhibit only the pentose phosphate shunt, markedly depressed TSH-induced formation of cyclic amp. These findings suggest that the pentose phosphate shunt might play an important role in triggering TSH stimulation of thyroid hormone secretion by supplying NADPH, and further, that NADPH dependency in thyroid hormone secretion is at a site prior to the generation of cyclic AMP.

6-Aminonicotinamide↗
PubMed1986

Center-specific variations of thyroid hormone serum levels in hemodialysis patients.

Thyroid hormone (free and total thyroxine, total 3,5,3'- and 3,3'5'-triiodothyronine, thyroxine-binding globulin, thyrotropin) serum concentrations were measured in 107 uremic patients of 4 hemodialysis centers, in order to study the prevalence of hypothyroidism in hemodialysis patients. In accordance with the clinical impression there was no laboratory evidence of thyroid dysfunction. In spite of the fact that all patients had the expected low-T3 syndrome, there were highly significant differences between the mean thyroid hormone concentrations of the 4 different centers. The center with the highest thyroid hormone levels (all normal except for borderline low 3,5,3'-triiodothyronine) also had the lowest urea levels, indicating the relatively best metabolic control. One center had significantly lower hormone levels than the other 3 centers (all hormones except free thyroxine were below normal) with urea levels that did not differ significantly from one of these centers. A retrospective analysis of patients and of the techniques of dialysis of 3 centers excluded factors like heparin or the length of time on dialysis to be the reason for the low values of this center. Finally, only the significantly higher proportion of unsuccessfully transplanted patients and some technical differences (lack of water treatment, regenerated cellulose as dialyser membrane, and low magnesium content in the dialysate) unique for this center remained as possible factors that may speculatively explain the observed low thyroid hormone values.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1998

Prostaglandin-independent stimulation of bone resorption in mouse calvariae and in isolated rat osteoclasts by thyroid hormones (T4, and T3).

The thyroid hormones, thyroxine (T4) and triiodothyronine (T3), were found to enhance both neonatal mouse calvarial bone resorption and pit formation on bovine slices by isolated rat osteoclasts. Dosage-dependent release of 45Ca from mouse calvarial bones was observed after 120 hr of culture with 10(-6)-10(-8) MT4 and 10(-6)-10(-10) M T3. Maximum treatment/control ratios of 45Ca release were recorded for 10(-7) M T4 and 10(-8) MT3. Inhibition of 45Ca release stimulated by 10(-8) M T3 was observed in the presence of 30 nM salmon calcitonin at 48 hr and 120 hr of culture with no indication of "escape" by T3-treated bones. In contrast, stimulation of 45Ca release from mouse calvarial bones by 10(-7) MT4 and 10(-8) MT3 was not inhibited by 10(-6) M indomethacin. Formation of PGE2 and PGI2 (evaluated by measuring 6-keto-PGF1alpha) by mouse calvariae was also not increased by 10(-8) MT3 after 120 hr of culture. Furthermore, no increases in cAMP formation were observed in calvarial bone cultures after either 10 min or 24 hr of exposure to 10(-8) MT3. However, significant inhibition of 45Ca release stimulated by 10(-8) M T3 was found at 120 hr in the presence of 10(-3) M hydroxyurea. When isolated rat osteoclasts were cultured in the presence of 10(-7) MT3, a 1.4-fold stimulation of pit number was observed. Pit formation was not affected by addition of 10(-6) M indomethacin to either the control or T3-treated cultures. These data suggest that the stimulation of bone resorption in neonatal mouse calvariae and activation of isolated rat osteoclasts by the thyroid hormones is not related to either prostaglandin or cAMP formation. In mouse calvariae, the effect on bone resorption of the thyroid hormones is dependent on increased cellular replication, perhaps of osteoclast precursors, or other bone cells involved in the resorptive process.

6-Ketoprostaglandin F1 alpha↗
PubMed1994

[Hyperthyroidism at elevated thyreostimulin. A case with pituitary resistance to thyroid hormones].

Simultaneous elevation of thyreostimulin and thyroid hormones values, when associated with clinical hyperthyroidism, raises a dual problem of diagnosis and treatment. We report a case of hyperthyroidism with elevated thyreostimulin in a young adult man. The values of free triiodothyronin and free thyroxin were elevated and the thyroxin binding globulin was normal. A normal pituitary tomodensitometry, the normal values of the alpha sub-unit of thyreostimulin and the dynamic tests of thyreostimulin secretion allowed us to rule out the hypothesis of a pituitary adenoma. Non-tumoral inappropriate secretions of thyreostimulin are at present regarded as syndromes of resistance to thyroid hormones. Their biological translation is a simultaneous elevation of thyreostimulin and thyroid hormones. Peripheral resistance, which is rarely complete, finds its expression in clinical hyperthyroidism or in normal clinical condition, whereas pituitary resistance, which causes the lack of feedback on the secretion of thyreostimulin expresses itself by clinical hyperthyroidism, sometimes with goitre owing to the trophic action of thyreostimulin on the thyroid. Generalized syndromes of resistance are the most common. Our patient had a selective pituitary resistance to thyroid hormones and less than thirty cases are reported in the literature. Treatment with a beta-blocker remains indicated when facing clinical evidence for hyperthyroidism and oral triiodothyronin seems to be able to slow down the inappropriate secretion of thyreostimulin. Regarding our patient who experienced a clinical and biological relapse after the stopping of the treatment, we join many authors who recommend a prolonged treatment.

Adult↗
PubMed2002

Thyroid hormone regulates neurotransmitter release in neonatal rat hippocampus.

Thyroid hormone is essential for the normal maturation and function of the mammalian CNS. Thyroid hormone deficiency during a critical period of development profoundly affects cognitive functions such as learning and memory. However, the possible electrophysiological alterations that could underlie these learning deficits in hypothyroid animals remain largely unexplored. In this work, we have studied the possible effect of thyroid hormone on short-term synaptic plasticity, which is hypothesized to be a neural substrate of short-term memory. We compared short-term modification of the excitatory postsynaptic potential in hippocampal slices between control and hypothyroid rats. Electrophysiological studies reveal that paired-pulse facilitation is strongly altered in the hypothyroid rats. In addition, hypothyroid rats exhibit an increase in the Ca(2+)-dependent neurotransmitter release. These alterations are basically reversible when thyroid hormone is administered. In order to examine the possible molecular mechanisms underlying these synaptic changes, we compared the expression of synapsin I, synaptotagmin I, syntaxin, and alpha-Ca(2+)/calmodulin kinase II between control and hypothyroid hippocampus. Our results show that the levels of synapsin I and synaptotagmin I are increased in the hypothyroid rats, which suggests that the genes encoding these proteins are implicated in the action of thyroid hormone on neurotransmitter release. Taken together, the results from this study suggest that thyroid hormone may modulate the probability of neurotransmitter release.

Adenosine↗
PubMed2003

Isometric force and endurance in skeletal muscle of mice devoid of all known thyroid hormone receptors.

The importance of thyroid hormone receptors for isometric force, endurance and content of specific muscle enzymes was studied in isolated slow-twitch soleus and fast-twitch extensor digitorum longus (EDL) muscles in mice deficient in all known subtypes of thyroid hormone receptors (i.e. TR alpha1, beta1, beta2 and beta3). The weights of soleus and EDL muscles were lower in TR-deficient (TRalpha1-/-beta-/-) mice than in wild-type controls. The force per cross-sectional area was not significantly different between TRalpha1-/-beta-/- and wild-type muscles. Soleus muscles of TRalpha1-/-beta-/- mice showed increased contraction and relaxation times and the force-frequency relationship was shifted to the left. Soleus muscles of TRalpha1-/-beta-/- mice were more fatigue resistant than wild-type controls. Protein analysis of TRalpha1-/-beta-/- soleus muscles showed a marked increase in expression of the slow isoform of the sarcoplasmic reticulum Ca2+ pump (SERCa2), whilst expression of the fast type (SERCa1) was decreased. There was also a major decrease in the alpha2-subunit of the Na+-K+ pump in TRalpha1-/-beta-/- soleus muscles. EDL muscles from TRalpha1-/-beta-/- and wild-type mice showed no significant difference in contraction and relaxation times, fatigue resistance and protein expression. In conclusion, the present data show changes in contractile characteristics of skeletal muscles of TRalpha1-/-beta-/- mice similar to those seen in hypothyroidism. We have previously shown that muscles of mice deficient in TRalpha1 or TRbeta display modest changes in muscle function. Thus, in skeletal muscle there seems to be functional overlap between TRalpha1 and TRbeta, so that the lack of one of the receptors to some extent can be compensated for by the presence of the other.

Animals↗
PubMed1990

Alterations of serum concentrations of thyroid hormones and sex hormone-binding globulin, nuclear binding of tri-iodothyronine and thyroid hormone-stimulated cellular uptake of oxygen and glucose in mononuclear blood cells from patients with non-thyroidal illness.

Nuclear tri-iodothyronine (T3) binding and thyroid hormone-stimulated oxygen consumption and glucose uptake were examined in mononuclear blood cells from patients with non-thyroidal illness (NTI) in which serum T3 was significantly (P less than 0.05) depressed (0.62 +/- 0.12 (S.D.) nmol/l) compared with healthy control subjects (1.45 +/- 0.30 nmol/l). Neither serum TSH nor sex hormone-binding globulin differed from that of the control group. Nuclear T3 binding capacity was increased (P less than 0.05) in patients with NTI (10.1 +/- 3.0 fmol/100 micrograms DNA) compared with controls (2.5 +/- 0.9 fmol/100 micrograms DNA). Unstimulated glucose uptake was increased in cells from patients with NTI (2.03 +/- 0.49 mmol/l per mg DNA per h, P less than 0.01) compared with controls (1.13 +/- 0.20 mmol/l per mg DNA per h). Thyroxine-stimulated glucose uptake (stimulated glucose uptake--unstimulated glucose uptake) was increased in cells from patients with NTI (2.06 +/- 1.67 mmol/l per mg DNA per h, P less than 0.01) compared with controls (0.26 +/- 0.12 mmol/l per mg DNA per h), and T3-stimulated glucose uptake was also increased in cells from patients with NTI (1.34 +/- 0.81 mmol/l per mg DNA per h, P less than 0.05) compared with controls (0.24 +/- 0.10 mmol/l per mg DNA per h). In contrast, neither unstimulated nor thyroid hormone-stimulated oxygen consumption differed. We conclude that both increased nuclear T3 binding and increased thyroid hormone-induced glucose uptake may represent counter-regulatory mechanisms which tend to maintain intracellular homeostasis.

Adult↗